In a previous phase 2 single-arm study that evaluated the efficacy of the combination of tucatinib plus trastuzumab and capecitabine in patients with HER2-positive breast cancer and newly diagnosed LMC, the median time to CNS progression was 6.9 months, and the median OS time was 11.9 months26. The gene discussed is ERBB2; the disease is breast carcinoma.